Before I discuss weed management in farm ponds, let me first alert you to the fact that a new noxious weed has been identified in North Carolina. This weed is not native to the United States and, if allowed to become established, can cause serious problems in ponds and in natural waterways such as the Lumber River.

Giant salvinia (Salvinia molesta) was first found in a water garden display at the State Fair a couple of years ago. Since then it has been found in several aquatic and wetland nurseries and in garden centers and aquarium dealerships that sell aquatic plants and water garden supplies. It is evident that this plant has escaped into natural waters, because it has been identified in several golf course ponds and a couple of storm-water retention ponds.

Giant Salvinia is a fern. Ferns are vascular plants and do not form flowers or seed; they reproduce by spores. Aquatic ferns are categorized with other aquatic plants as those that grow submerged below water, float freely on top of water, or grow with foliage partly or entirely emergent from the water surface.

Most noxious weeds that become established in North Carolina do so because of situations such as with this weed. They are purchased as ornamental or specialty plants with no knowledge that they are noxious and then either escape into the surrounding environment or are discarded. As they find their way into suitable environments, they usually grow unchecked until they begin to cause serious problems.

If you spend any time at all around water in our county, I would like to encourage you to be especially observant for this weed. Please pay close attention to any pond weed that looks unusual, especially in water gardens or frequently used ponds. If you see a plant that looks suspicious, please give me a call (910-671-3276).

If properly constructed, good pond management will most times prevent aquatic weeds from becoming a problem. Water in ponds should be at least three feet deep, and the water color should be maintained to prevent sunlight from penetrating more than 18 inches into the water. When sunlight cannot penetrate to the soil beneath the water, most aquatic will never become established.

Proper fertilization is one method of maintaining water color. Fertilizer encourages the growth of single cell algae which is the first link in the food chain. This algae provides the color needed to filter out sunlight. However, caution should be used when fertilizing farm ponds, because improper timing and applications of fertilizer can often encourage unwanted weed species to get out of hand.

Many pond owners can use commercial dyes to give color to water. This is the same dye used in small ponds and ornamental fountains such as theme parks and apartment complexes. The dye has no harmful effect to the fish or to those using the pond; they simply filter out the sunlight.

Certain species of carp can also be used as a biological control for aquatic weeds. Sterile grass carp consume a large amount of vegetation and, under most conditions, can provide adequate weed control in ponds for many years.

If aquatic weeds are allowed to get out of hand, it is often very difficult and very expensive to get them under control using chemical herbicides. It is not uncommon for herbicide applications in farm ponds costing $400 or more per acre.

For more information about aquatic weed management, please give me a call. If you have a farm pond, I encourage you to try to identify weed problems before they become severe and to develop and carry out a good pond management plan.

E-mail address: Everett_Davis@ncsu.edu

Mailing Address:
P. O. Box 2280
Lumberton, NC 28359-2280

Phone: 910-671-3276
Fax: 910-671-6278

Date Created 3/11/03